1. Field of the Invention
The present invention relates to a method of optical proximity correction (OPC), and more particularly, to a method of OPC including modifying a corrected layout pattern according to an original layout pattern, wherein the corrected layout pattern is the layout pattern modified through the OPC method.
2. Description of the Prior Art
In semiconductor manufacturing processes, the integrated circuit layout is first designed and formed as a mask pattern. The mask pattern is then proportionally transferred to a target layer such as photoresist layer disposed on the semiconductor wafer through an exposure process followed by a development process. Subsequently, a corresponding etching process is performed in order to manufacture the semiconductor devices on the semiconductor wafer.
With the demands of increasing integration and decreasing size of the semiconductor devices, the critical dimension (CD) of each segment fabricated through exposure is limited to the resolution limit of the optical exposure tool used for transferring the mask pattern. A problem that easily arises during the exposures of a mask pattern with high-density arranged segments to form a pattern on a photoresist is the optical proximity effect. Such a resolution loss occurs because of overexposure or underexposure, which brings a deviation of the pattern on the photoresist layer from the original mask pattern.
Many saving methods have been used to avoid the deviation caused by the optical proximity effect in order to improve the quality of the transferred pattern. The most popular method is the optical proximity correction (OPC). And there is a variety of commercial optical proximity correction softwares that can theoretically correct the mask patterns to be more accurately transferred on a wafer. Additionally, the double patterning technique (DPT) has been developed and taken as one of the most promising lithographic technologies for 32 nanometer (nm) node and 22 nm node patterning processes for overcoming the limitations of the conventional optical exposure tools. The DPT includes a photolithography-etch-photolithography-etch approach, also called 2P2E, or a photolithography-photolithography-etch approach, also called 2P1E. The first photolithography process and the second photolithography process are performed to form the respective patterns in the target layer through different masks, which may jointly form the predetermined layout pattern.
In the illustrated DPT, the original layout pattern is usually divided into two different masks, and a pattern density of the pattern predetermined to be formed in each of the photolithography processes is different from a pattern density of the original layout pattern; so the OPC methods respectively performed on the patterns of the two different masks may therefore cause excessive adjustment on the mask patterns, and the patterns later formed in the target layer through the two masks may not be combined to form the accurate layout pattern. For example, an unexpected bridge can be formed. Consequently, how to improve the method of optical proximity correction (OPC) to form the accurate layout pattern, is still an important issue in the field.